1. Field of the Invention
The present invention relates to the field of disk drives. In particular, the present invention relates to a microactuator for a disk drive that reduces off-track motion of a read/write element.
2. Description of the Related Art
FIG. 1 shows an exemplary high-RPM hard disk drive (HDD) 100 having a magnetic read/write head (or a recording slider) 101 that includes, for example, a tunnel-valve read sensor, that is positioned over a selected track on a magnetic disk 102 using, for example, a two-stage servo system for reading data stored on disk 102. The two-stage servo system includes a voice-coil motor (VCM) 104 for coarse positioning a read/write head suspension 105 and may include a microactuator, or micropositioner, for fine positioning read/write head 101 over the selected track. As used herein, a microactuator (or a micropositioner) is a small actuator that is placed between a suspension and a slider, and moves the slider relative to the suspension.
FIG. 2 depicts a conventional suspension and microactuator arrangement 200. Suspension and microactuator 200 includes a suspension 201, a microactuator 205 and a slider 209. Suspension 201 includes a load beam 202, a dimple 203 and a flexure 204. Suspension 201 imparts a loading force (gram-load) to slider 209. Suspension 201 also provides pitch and roll freedom of motion to the parts attached to suspension 201 by using dimple 203, which is a hemispheric-shaped bump that is made on load-beam 202 and makes a point contact to flexure 204. Flexure 204 is designed to have an extremely low stiffness in roll and pitch direction, and to have an accurately defined free-state both in roll and pitch directions, usually referred to as Pitch Static Attitude (PSA) and Roll Static Attitude (RSA).
Microactuator 205 includes a substrate 206, a microactuator structure 207, and at least one flexure element 208. Substrate 206 is the stationary structure of microactuator 205. Microactuator structure 207 is the movable structure of microactuator 205. Microactuator 205 is usually designed to move horizontally (either rotational or translational) so that the position of slider 209 attached to microactuator 205 can be changed. Microactuator 205 must be designed to have very high stiffness in the z-axis direction and in the pitch/roll direction. These requirements are usually fulfilled by designing a spring structure 208 inside microactuator 205 that is especially anisotropic.
Slider 209 includes a read/write element 210 and is identical to the sliders that are typically used in non-microactuator-type HDDs.
One problem associated with conventional microactuators is that external forces, such as airflow, cause movement of the microactuator in the roll directions, thereby causing read/write element tracking inaccuracies. FIG. 3 depicts movement of microactuator 200 in roll directions 311 under the influence of external forces, such as airflow, as microactuator 200 moves over disk 312. Movement in roll directions 311 causes tracking inaccuracies, as depicted by arrow 313.
Another problem associated with conventional microactuators is that the electrical connections between a suspension and a microactuator are particularly difficult to make. There are two conventional ways for making the electrical connection. First, a bent-lead connection technique can be used, or second, a sidewall-bonding-pad connection technique can be used.
FIG. 4 depicts a conventional bent-lead connection technique for making an electrical connection between a conventional microactuator and a suspension. The microactuator structural arrangement shown in FIG. 4 corresponds to the suspension and microactuator structural arrangements shown in FIGS. 2 and 3. A dimple 403 is formed on a suspension 401 and makes a point contact to a flexure (not shown in FIG. 4). A microactuator 405 is attached to the flexure. A slider 409 is attached to microactuator 405. A bent lead 415 is electrically connected to a solder ball 416 and a bonding pad 417 to microactuator 405. Another solder ball 418 is shown for one of the connections to read/write head (not shown in FIG. 4) on slider 409 for another bent-lead connection that is not visible in FIG. 4.
The problems associated with a bent-lead connection technique includes that a bent-lead suspension is expensive and difficult to make. It is also difficult to control PSA and RSA after the terminations are made. Further, the solder-bump connections must be made from the opposite side and the terminations cannot be formed from leading-edge side of the microactuator and slider otherwise pitch stiffness becomes too high.
FIG. 5 depicts a conventional sidewall-bonding-pad connection technique for making an electrical connection between a conventional microactuator and a suspension. The microactuator structural arrangement shown in FIG. 5 also corresponds to the microactuator structural arrangements shown in FIGS. 2 and 3. A dimple 503 is formed on a suspension 501 and makes a point contact to a flexure (not shown in FIG. 5). A microactuator 505 is attached to the flexure. A slider 509 is attached to microactuator 505. A side-wall-bonding pad 515 is electrically connected through a solder ball 516 to microactuator 505. Another solder ball 518 is shown for one of the connections to read/write head (not shown in FIG. 5) on slider 509 for another side-wall bonding pad connection that is not visible in FIG. 5.
The problems associated with a sidewall-bonding-pad connection technique includes that it is extremely difficult to make bonding pads on the sidewall of a microactuator.
There is a difficulty in controlling PSA/RSA and dimple-contact position that is commonly experiences with conventional non-microactuator Head Gimbal Assemblies (HGAs). Currently, the PSA/RSA of a suspension and dimple-contact position must be controlled very accurately using conventional sheet-metal machining techniques, such as stamping and folding, for properly maintaining the fly-height of the slider. The dimple is usually hemispherically shaped and has a large diameter so it is very difficult to define the contact point of the dimple tip to the flexure. This problem is particularly acute when a contact slider having a very low stiffness is used.
Yet another problem with conventional microactuators occurs when the vertical distance between the dimple-contact point (at the center of rotation) to the Read/Write element is relatively large, the off-track motion caused by disk tilt (usually caused by disk vibration) becomes proportionally larger. When a conventional microactuator is used, the vertical distance increases by the thickness of a microactuator. Accordingly, the off-track motion increases.
What is needed is a suspension and microactuator arrangement that overcomes the drawbacks of a conventional suspension and microactuator, such as PSA/RSA of the suspension and microactuator arrangement, dimple-contact position and electrical connections between the suspension and the microactuator.